Stator vane assembly



April 1967 w. E. HOWALD 3,314,648

STA'IOR YANE ASSEMBLY Filed Dec. 19, 1961 INVENTOR. fife/Y5? E 6 0/1641 BY fine-M QFM L United States Patent 3,314,648 STATOR VANE ASSEMBLY Werner Ernst Howald, Cincinnati, Ohio, assignor to General Electric Company, a corporation of New York Filed Dec. 19, 1961, Ser. No. 160,668 1 Claim. (Cl. 253--39.1)

The present invention relates to a stator vane assembly and more specifically to a lightweight simplified assembly for supporting the stator vanes in the hot primary gas flow of a turbomachine.

In present day turbomachines, and especially in aircraft gas turbines, the present design trends are in the direction of lightweight simplified assemblies which are capable of withstanding the higher and higher primary flow temperatures. Of course, along with the higher temperatures encountered are higher gas pressures which must .be eflFectivcly retained within the primary gas flow areas. Naturally, to economize on weight of such an assembly, maximum efficiency of the structures must be attained by taking full benefit of the physical properties of the materials utilized.

In stator vane assemblies where it is necessary to maintain the stator vanes directly in the primary gas flow, both the physical forces on the assembly and the temperatures encountered become major problems. Since the vanes extend through the gas flow, substantial axial and tangential forces are imposed on the assembly which must be reacted by the stator vane support. Additionally, problems arise in providing for expansion of the stator assembly due to its being exposed to the extremely high temperature gases. This exposure is present whether it be due to the combustion of fuel upstream of the turbine or to temperature rises in a compressor. In attempting to limit this radial expansion, provision has been made in the past for the flow of cooling air through the stator vane support and stator vanes, however this in itself adds additional complications in that provision must be made for ducting this cooling air.

Naturally, to provide the lightweight structure for supporting these stator vanes, a one-piece annular support at each end of the vanes would be beneficial in providing an integrated structure while minimizing leakage through the support assembly. However, problems of non-uniform expansion have occurred in the past, resulting in abnormal stresses and warpage within the assembly. Also, the use of a one-piece support has complicated the cooling of the assembly as openings therethrough for cooling fluid flow defeat the overall structural efiiciency and integrity of such a support.

Accordingly, it is one object of this invention to provide a simplified lightweight stator vane support for a turbomachine.

It is another object of this invention to provide such a stator v-ane support capable of operation in high temperature machines without harmful efiects to the support.

It is a further object of this invention to provide such a simplified stator vane support with means for introducing cooling air within the support, and into the stator vanes for operation in high temperature turbomachines.

In accordance with one aspect of the invention, there is provided a stator vane assembly for use in a turbomachine having a primary annular gas flow passageway comprising a plurality of stator vanes extending across the gas passageway and supported on the inner and outer ends thereof, respectively, by a thin one-piece annular member which extends radially and axially from the which join turbomachine supporting structure to which it is attached to the farthest axially removed edge of that end of the vanes. These support members have substantially equal wall thickness and allow for radial expansion of the vanes without undue internal stresses being generated within the assembly. Furthermore, by the support members intersecting the vanes at the farthest axially removed edge from the turbomachine supporting point or attachment, the support members serve as wall members for the cooling air passageways so that provision need not be made for the passage of the cooling air through the support members.

The invention will be lowing description taken panying drawings and its appended claim.

In the drawing:

FIG. 1 is a cross-sectional view incorporating the present invention,

FIG. 2 is a cross-sectional view along the lines 2-2 of FIG. 1 showing the engine cross-section.

Referring now to the drawings, therein is illustrated a turbomachine section having an outer casing member or wall 11. Located within the casing 11 are concentric flow guiding means 12 and 13 defining an annular primary gas flow passage 15 through which the primary engine flow passes in the direction denoted by the arrow 16. Extending across this annular gas passageway 15 are a plurality of stator vanes 17 which direct the primary gas flow so that it strikes the plurality of rotor vanes 18 mounted on the periphery of rotor wheel 19 at the correct angle for optimum rotation of the rotor wheel by the primary gas. A shroud 22 located at the outer ends of the rotor blades 18 reduces the amount of primary gas leakage around the rotor blades, this shroud being supported by the shroud support member 23 extending from the outer casing joint 24. (Although the shroud could also be directly attached to the member 43.) An additional labyrinth seal 26 is provided consisting of a stationary honeycomb 27 supported from the seal support 28 with a cooperating rotating seal member 29 supported from the rotor wheel 19.

Turning now to the stator vane support assembly, the stator vanes 17 are initially attached or interlocked to a pair of one-piece concentric ring members 33 and 34 and form an extension of the inner and outer flow defining means or members 12 and 13 respectively, to contain the primary gas flow. The ring member 34 joins the inner member 13 through a slip joint or tonguein-groove joint 35to allow for axial movement between the members. Further these ring members are made of thin material to allow flexing [for radial movement of the vanes as will be described hereinafter. Ring member 33 forms a radially extending slip joint with insert 36 which in turn forms an axially extending slip joint with the outer member 12. In this manner both radial and axial movement is permitted between the primary flow guiding means 12 and 13 and stator vane assembly and in addition, the former may be removed if need be without removal of the stator vane assembly. Members 33 and '34 are of thin-walled construction of substantially equal thickness so that both will heat up and cool down in about the same time and therefore remain at substantially equal temperature when exposed to the hot primary gas flow. This limits internal stressing within the stator vane assembly by equalizing the expansion between these two members and between the vanes and these members. Also,

better understood from the folin connection with the accomscope will be pointed out in the of a stator assembly 'require a brazed joint since these members are one-piece members, leakage of gas from the primary flow duct is minimized as no saw cuts exist through which gas leakage can occur and which are usually necessary to allow for differential expansion in the support assembly. It has been found that where there is local gas leakage, the gas passes through the opening at high velocities and the heat exchange coefficient is high; this results in excessive heating at these local points and the resulting local stressing may result in warping the components at that point.

The stator vanes 17 extend through openings 38 in the member 33 and openings 39 in the member 34 and are hollow to permit the internal flow of a cooling fluid. By extending through the members 33 and 34 in this manner the vane extensions form cooling fluid passages for ducting cooling air into the interior of the vane from the stator assembly support area. The vane may also be provided with a portion 40 which abuts these members 33 and 34 to provide additional support for the vane and allow for a more firm attachment to the stator vane support rings as will be pointed out later.

The stator vanes may be unattached but accurately fitted in the supports or may be brazed or otherwise attached in the manner illustrated to the members 33 and 34. A simple method of assembly is suitable wherein the outer member 33 is heated and the stator vanes 17 and inner member 34 are cooled to cause the resulting contraction and expansion with the vanes 17 being inserted between these annular members at these temperatures. Upon allowing the components to return to ambient temperature it has been found that a very satis factory and rigid structure is provided which does not between the vanes and these members.

To support this stator vane in the turbomachine, generally cone shaped one-piece support members 43 and 44 are provided. Truncated cone shaped support member 43 extends from the casing joint 24 in a radial and axial direction to the downstream or farthest removed in the axial direction (i.e., the trailing) edge of the stator vane 17 where it supports the stator vane assembly by attachment to the member 33 at this point. Similarly, support member 44 extends from an inner engine casing structure 45 in a radial and axial direction to the farthest axial or downstream edge of stator vane 17 where it is attached to member 34 and the stator vane 17 at this point. It can be seen that the support members 43 and 44 are thin annular members of substantially the same thickness. In the embodiment shown, the members are primarily in tension in reacting the axial forces imposed on the stator vanes by the primary gas flow 16 thereby making optimum use of the material and providing an eflicient lightweight structure. In addition, by making the members relatively thin-walled and by locating them so that they extend in a radial and axial direction, both the stator vanes 17 and the ring members 33 and 34 which are of substantially equal thick: ness to the support members may expand radially due. to temperature increases and not affect the stator support members by causing excessive internal stressing in the support. Since all support members are of substantially equal thickness, they in turn will expand equally at the same time thereby taking up the expansion of the stator vane assembly equally which results in less internal stressing within the overall vane assembly which might result in using such oneapiece support members.

As mentioned heretofore, provision is made for circulating cooling fluid through the hollow stator vane 17 as denoted by the arrows 47 and 48. The cooling fluid passes from the upstream direction and is ducted between the outer casing member 11 and the outer flow defining member 12 to a passageway formed only by the stator support components 43 and 33 and subsequently into the blade 17 to be discharged on the downstream edge in some suitable manner as denoted by the arrows 49. Similarly, as denoted by arrows 48, cooling fluid may pass either from the interior of the engine or in the passageway formed by the inner casing wall 45 and the inner flow defining member 13 to pass into the interior of the blade as guided by stator support components 34 and 44. By attaching the support members 43 and 44 at the downstream or far edges of that end of the stator vanes, no openings need be provided through the stator vane support for the passage of cooling fluid thereby providing for a lightweight rigid structure to react the forces imposed on the support while still being flexible in the manner necessary to allow for thermal expansion of the structure. Also, the stator vane support members serve as cooling flow passage walls which does away with the use of additional wall members or piping to guide the cooling fiow and further, completely bathes the support members by the cooling flow thereby maintaining them at a reasonable temperature to equalize expansion thereof and to prevent their undue exposure to high temperatures. It should be noted at this point that while the support members have been illustrated as extending from the upstream direction to the stator vanes, it is equally possible that the support members could also extend downstream from the downstream side of the vanes in a similar manner and by placing the members in compression, an efficient and somewhat similar structure could be provided.

While a particular embodiment of the invention has been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention and it is intended to cover in the appended claim all such changes and modifications that come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Lett rs Patent of the United States is:

A stator vane assembly for a tubomachine comprising;

a pair of concentric inner and outer flow guiding members defining an annular primary gas flow passage therebetween;

inner and outer casing members surrounding their respective flow-guiding members in spaced relationship thereto to provide secondary cooling fluid passageways;

a plurality of stator vanes having internal cooling fluid passages in flow communication with openings in the radially spaced vane ends, said vanes extending transversely of said primary flow passage and being attached at said ends to said flow guiding members adjacent the trailing edges of said vanes whereby said ends extend at least partially through openings in said flow guiding members adjacent the leading edges of said vanes;

an outer stator vane support comprising a first onepiece thin-walled generally conical member having one edge thereof affixed to said outer casing member, the other edge of said conical member being spaced radially and axially from said one edge and being aflixed to said outer flow guiding member adjacent said trailing edges;

an inner stator vane support comprising a second onepiece thin-walled generally conical member having one edge thereof affixed to said inner casing member, the other edge of said conical member being spaced radially and axially from said one edge and being aflixed to said inner flow guiding member adjacent said trailing edges;

said flow guiding and said conical members. being of substantially equal thickness to minimize differential thermal expansion in said assembly;

and means to supply cooling fluid to said secondary flow passageways for circulation through said stator vanes to cool said vanes and said conical support members.

(References on following page) 6 References Cited by the Examiner 2,937,000 5/ 1960 Ledwith 253-78 UNITED STATES PATENTS 2,968,467 1/1961 McGregor 25378 MARTIN P. SCHWADRON, Primary Examiner.

Constant et a1. 60-3932 Mierley et a1. 5 SAMUEL FEINBERG, BENJAMIN A. BORCHELT, Wheatley et a1. 25349.1 X Exammm- Petrie et a1. 253-39.1 S. W. ENGLE, E. A. POWELL, JR.,

Nichols 253-78 Assistant Examiners. 

